1. Field of the Invention
The present invention relates to a semiconductor module and, more particularly, to a semiconductor module having a plurality of stacked circuit elements and a mobile apparatus mounting the semiconductor module thereon.
2. Description of the Related Art
Recently, a packaging technology known to realize smaller size and functional sophistication for circuit devices used in electronic equipment is a multilayer stack structure (multi-chip package structure) capable of mixed packaging of a plurality of circuit elements. With circuit devices of multilayer stack structure, however, mixed packaging by stacking, for instance, a circuit element comprising an analog circuit and a circuit element comprising a digital circuit may present problems. For example, the high-frequency noise (noise containing high-frequency components) occurring in the circuit element having a digital circuit operating at high speed can be propagated to the circuit element having an analog circuit which is likely to be affected by the noise, and thereby interferes with the performance of the circuit element having the analog circuit. This destabilizes the operation of the circuit device, thus lowering the reliability thereof.
As a countermeasure to such noise propagation, for example, a technology is known wherein noise propagation between circuit elements is intercepted by inserting a heat-transmitting conductor (metallic plate), which is held at ground potential, between a semiconductor chip comprising an analog circuit (circuit element having an analog circuit) and a semiconductor chip comprising a digital circuit (circuit element having a digital circuit).
Also, a technology is known wherein an aerial circuit (antenna) of metallic wiring, which is provided in the outer periphery of an electromagnetic radiation source (a circuit element having a digital circuit), absorbs unwanted radiation (noise) therefrom, thus controlling the noise propagation from the electromagnetic radiation source.
With the method according to the former known technology, however, potential variation can occur within the plane of the metallic plate due to the noise (especially the noise containing high-frequency components) propagating from the circuit element having a digital circuit to the metallic plate. And during the process of the potential variation propagating to a grounding link (ground point) via the metallic plate, the potential variation can enter as noise into the circuit element having an analog circuit which is in the propagation path.
The method according to the latter known technology may be effective if the circuit element having a digital circuit and the circuit element having an analog circuit are placed side by side on the same plane. But it may not function effectively to control noise in the vertical direction between the circuit elements if a multilayer stack structure is employed with the circuit elements provided with antennas in the outer periphery thereof stacked one on top of the other.